The PC/Mac market will continue to fall as the "average" user (eg those with no interest in technology at all, but obviously everyone needs to use the internet) just use their phones for everything. A large majority of people I know on Twitter only every use their phone for all their computing needs, they have a laptop which is opened once every couple of months - they're not even on tablets, just phones.
It's alien to me, someone who spends 10+ ours a day on a Mac and rarely uses my phone for anything but thats what "the man in the street" is doing.
I am in exactly the same position where I am always on my MacBook and do not use my iPhone much at all. When some Android people tell me that they cannot use an iPhone because it does not let them do X, Y and Z, my response is that I do those things on a laptop running a proper OS.